1. Field of the Invention
The present invention relates to a substrate processing apparatus for conducting liquid processing of various types of substrates, such as semiconductor wafers, or glass substrates of liquid crystal panels, etc. More particularly, the present invention relates to a substrate processing apparatus for distributing and supplying processing liquid from a common processing liquid supply unit to a plurality of processing units.
2. Description of the Prior Art
Manufacturing processes of semiconductors or liquid crystal panels include liquid processing, for example, cleaning or etching. Liquid processing includes emitting processing liquid to a target object or dipping a target object in processing liquid Substrate processing apparatuses can be used to automatically conduct liquid processing. Substrate processing apparatuses have a plurality of liquid processing units to conduct liquid processing of substrates, a processing liquid supply unit to supply a processing liquid to the liquid processing units, included in a common case, a cassette connected to the common case, and a substrate carrying unit to carry in/out target substrates between the cassette and the liquid processing units.
Substrate processing apparatuses supply processing liquid from a common processing liquid supply unit to a plurality of liquid processing units. A processing liquid supply unit has a processing liquid combination tank to combine stock solutions supplied from a plurality of stock solution sources to produce processing liquid In some cases, a processing liquid reservoir may be used to contain the processing liquid supplied from the processing liquid combination tank and to distribute and supply the processing liquid to the liquid processing units. A return channel may be also used to return residual processing liquid, i.e. a part of the processing liquid that has not been used by the liquid processing units, to the processing liquid reservoir. An example of returning the residual processing liquid is disclosed in Japanese Laid-open Patent Publication No. 2007-109738, the disclosure of which is incorporated herein by reference in its entirety.
Further, substrate processing apparatuses also have a sensor installed in the processing liquid supply unit to detect the amount of the remaining processing liquid. Thus, if no processing liquid exists in the processing liquid supply unit, the apparatus is shut down.
However, if a substrate processing apparatus is enforced to shut down for lack of the processing liquid remaining in the processing liquid supply unit, the liquid processing of substrates is suspended until the processing liquid supply unit is replenished with the processing liquid. This degrades the throughput of the substrate processing apparatus.
Furthermore, if a substrate processing apparatus is enforced to shut down, all the substrates existing in the liquid processing units will be defective. As a result, a yield ratio is decreased.
In some cases, even if no processing liquid exists in the processing liquid supply unit the processing liquid remaining in the pipe between the processing liquid supply unit and the liquid processing units may be used to complete processing of substrates existing in the liquid processing units. Furthermore, the processing liquid returning from the liquid processing units to the processing liquid reservoir via the return channel may be used to feed an operating liquid processing unit.